ISO/TC 85/SC 2/WG 2 - Reference radiations fields

This document specifies additional procedures and data for the calibration of dosemeters and doserate meters used for individual and area monitoring in radiation protection. The general procedure for the calibration and the determination of the response of radiation protection dose(rate)meters is described in ISO 29661 and is followed as far as possible. For this purpose, the photon reference radiation fields with mean energies between 8 keV and 9 MeV, as specified in ISO 4037-1, are used. In Annex D some additional information on reference conditions, required standard test conditions and effects associated with electron ranges are given. For individual monitoring, both whole body and extremity dosemeters are covered and for area monitoring, both portable and installed dose(rate)meters are covered. Charged particle equilibrium is needed for the reference fields although this is not always established in the workplace fields for which the dosemeter should be calibrated. This is especially true at photon energies without inherent charged particle equilibrium at the reference depth d, which depends on the actual combination of energy and reference depth d. Electrons of energies above 65 keV, 0,75 MeV and 2,1 MeV can just penetrate 0,07 mm, 3 mm and 10 mm of ICRU tissue, respectively, and the radiation qualities with photon energies above these values are considered as radiation qualities without inherent charged particle equilibrium for the quantities defined at these depths. This document also deals with the determination of the response as a function of photon energy and angle of radiation incidence. Such measurements can represent part of a type test in the course of which the effect of further influence quantities on the response is examined. This document is only applicable for air kerma rates above 1 µGy/h. This document does not cover the in-situ calibration of fixed installed area dosemeters. The procedures to be followed for the different types of dosemeters are described. Recommendations are given on the phantom to be used and on the conversion coefficients to be applied. Recommended conversion coefficients are only given for matched reference radiation fields, which are specified in ISO 4037-1:2019, Clauses 4 to 6. ISO 4037‑1:2019, Annexes A and B, both informative, include fluorescent radiations, the gamma radiation of the radionuclide 241Am, S-Am, for which detailed published information is not available. ISO 4037-1:2019, Annex C, gives additional X radiation fields, which are specified by the quality index. For all these radiation qualities, conversion coefficients are given in Annexes A to C, but only as a rough estimate as the overall uncertainty of these conversion coefficients in practical reference radiation fields is not known. NOTE The term dosemeter is used as a generic term denoting any dose or doserate meter for individual or area monitoring.

This document gives guidelines on additional aspects of the characterization of low energy photon radiations and on the procedures for calibration and determination of the response of area and personal dose(rate)meters as a function of photon energy and angle of incidence. This document concentrates on the accurate determination of conversion coefficients from air kerma to Hp(10), H*(10), Hp(3) and H'(3) and for the spectra of low energy photon radiations. As an alternative to the use of conversion coefficients the direct calibration in terms of these quantities by means of appropriate reference instruments is described.

This document specifies the characteristics and production methods of X and gamma reference radiation for calibrating protection-level dosemeters and doserate meters with respect to the phantom related operational quantities of the International Commission on Radiation Units and Measurements (ICRU)[5]. The lowest air kerma rate for which this standard is applicable is 1 µGy h?1. Below this air kerma rate the (natural) background radiation needs special consideration and this is not included in this document. For the radiation qualities specified in Clauses 4 to 6, sufficient published information is available to specify the requirements for all relevant parameters of the matched or characterized reference fields in order to achieve the targeted overall uncertainty (k = 2) of about 6 % to 10 % for the phantom related operational quantities. The X ray radiation fields described in the informative Annexes A to C are not designated as reference X-radiation fields. NOTE The first edition of ISO 4037-1, issued in 1996, included some additional radiation qualities for which such published information is not available. These are fluorescent radiations, the gamma radiation of the radionuclide 241Am, S-Am, and the high energy photon radiations R-Ti and R-Ni, which have been removed from the main part of this document. The most widely used radiations, the fluorescent radiations and the gamma radiation of the radionuclide 241Am, S-Am, are included nearly unchanged in the informative Annexes A and B. The informative Annex C gives additional X radiation fields, which are specified by the quality index. The methods for producing a group of reference radiations for a particular photon-energy range are described in Clauses 4 to 6, which define the characteristics of these radiations. The three groups of reference radiation are: a) in the energy range from about 8 keV to 330 keV, continuous filtered X radiation; b) in the energy range 600 keV to 1,3 MeV, gamma radiation emitted by radionuclides; c) in the energy range 4 MeV to 9 MeV, photon radiation produced by accelerators. The reference radiation field most suitable for the intended application can be selected from Table 1, which gives an overview of all reference radiation qualities specified in Clauses 4 to 6. It does not include the radiations specified in the Annexes A, B and C. The requirements and methods given in Clauses 4 to 6 are targeted at an overall uncertainty (k = 2) of the dose(rate) value of about 6 % to 10 % for the phantom related operational quantities in the reference fields. To achieve this, two production methods are proposed: The first one is to produce "matched reference fields", whose properties are sufficiently well-characterized so as to allow the use of the conversion coefficients recommended in ISO 4037-3. The existence of only a small difference in the spectral distribution of the "matched reference field" compared to the nominal reference field is validated by procedures, which are given and described in detail in ISO 4037‑2. For matched reference radiation fields, recommended conversion coefficients are given in ISO 4037‑3 only for specified distances between source and dosemeter, e.g., 1,0 m and 2,5 m. For other distances, the user has to decide if these conversion coefficients can be used. If both values are very similar, e.g., differ only by 2 % or less, then a linear interpolation may be used. The second method is to produce "characterized reference fields". Either this is done by determining the conversion coefficients using spectrometry, or the required value is measured directly using secondary standard dosimeters. This method applies to any radiation quality, for any measuring quantity and, if applicable, for any phantom and angle of radiation incidence. In addition, the requirements on the parameters specifying the reference radiations depend on the definition depth in the phantom, i.e., 0,07 mm, 3 mm and 10 mm, therefore, the requirements a

This document specifies the procedures for the dosimetry of X and gamma reference radiation for the calibration of radiation protection instruments over the energy range from approximately 8 keV to 1,3 MeV and from 4 MeV to 9 MeV and for air kerma rates above 1 µGy/h. The considered measuring quantities are the air kerma free-in-air, Ka, and the phantom related operational quantities of the International Commission on Radiation Units and Measurements (ICRU)[2], H*(10), Hp(10), H'(3), Hp(3), H'(0,07) and Hp(0,07), together with the respective dose rates. The methods of production are given in ISO 4037-1. This document can also be used for the radiation qualities specified in ISO 4037-1:2019, Annexes A, B and C, but this does not mean that a calibration certificate for radiation qualities described in these annexes is in conformity with the requirements of ISO 4037. The requirements and methods given in this document are targeted at an overall uncertainty (k = 2) of the dose(rate) of about 6 % to 10 % for the phantom related operational quantities in the reference fields. To achieve this, two production methods of the reference fields are proposed in ISO 4037-1. The first is to produce "matched reference fields", which follow the requirements so closely that recommended conversion coefficients can be used. The existence of only a small difference in the spectral distribution of the "matched reference field" compared to the nominal reference field is validated by procedures, which are given and described in detail in this document. For matched reference radiation fields, recommended conversion coefficients are given in ISO 4037-3 only for specified distances between source and dosemeter, e.g., 1,0 m and 2,5 m. For other distances, the user has to decide if these conversion coefficients can be used. The second method is to produce "characterized reference fields". Either this is done by determining the conversion coefficients using spectrometry, or the required value is measured directly using secondary standard dosimeters. This method applies to any radiation quality, for any measuring quantity and, if applicable, for any phantom and angle of radiation incidence. The conversion coefficients can be determined for any distance, provided the air kerma rate is not below 1 µGy/h. Both methods require charged particle equilibrium for the reference field. However this is not always established in the workplace field for which the dosemeter shall be calibrated. This is especially true at photon energies without inherent charged particle equilibrium at the reference depth d, which depends on the actual combination of energy and reference depth d. Electrons of energies above 65 keV, 0,75 MeV and 2,1 MeV can just penetrate 0,07 mm, 3 mm and 10 mm of ICRU tissue, respectively, and the radiation qualities with photon energies above these values are considered as radiation qualities without inherent charged particle equilibrium for the quantities defined at these depths. This document is not applicable for the dosimetry of pulsed reference fields.

ISO/TS 18090-1:2015 is directly applicable to pulsed X-radiation with pulse duration of 0,1 ms up to 10 s. This covers the whole range used in medical diagnostics at the time of publication. Some specifications may also be applicable for much shorter pulses; one example is the air kerma of one pulse. Such a pulse may be produced, e.g. by X-ray flash units or high-intensity femtosecond-lasers. Other specifications are not applicable for much shorter pulses; one example is the time-dependent behaviour of the air kerma rate. This may not be measurable for technical reasons as no suitable instrument is available, e.g. for pulses produced by a femtosecond-laser. ISO/TS 18090-1:2015 specifies the characteristics of reference pulsed radiation for calibrating and testing radiation protection dosemeters and dose rate meters with respect to their response to pulsed radiation. The radiation characteristics includes the following: a) time-dependent behaviour of the air kerma rate of the pulse; b) time-dependent behaviour of the X-ray tube high voltage during the pulse; c) uniformity of the air kerma rate within a cross-sectional area of the radiation beam; d) air kerma of one radiation pulse; e) air kerma rate of the radiation pulse; f) repetition frequency. ISO/TS 18090-1:2015 does not define new radiation qualities. Instead, it uses those radiation qualities specified in existing ISO and IEC standards. This part of ISO/TS 18090 gives the link between the parameters for pulsed radiation and the parameters for continuous radiation specifying the radiation qualities. It does not specify specific values or series of values for the pulsed radiation field but specifies only those limits for the relevant pulsed radiation parameters that are required for calibrating dosemeters and dose rate meters and for determining their response depending on the said parameters. The pulse parameters with respect to the phantom-related quantities were determined using conversion coefficients according to ISO 4037 (all parts). This is possible as the radiation qualities specified in existing ISO and IEC standards are used. A given reference pulsed X-ray facility is characterized by the parameter ranges over which the full specifications and requirements according to this part of ISO/TS 18090 are met. Therefore, not all reference pulsed X-ray facilities can produce pulses covering the same parameter ranges.

ISO 29661:2012 defines terms and fundamental concepts for the calibration of dosemeters and equipment used for the radiation protection dosimetry of external radiation -- in particular, for beta, neutron and photon radiation. It defines the measurement quantities for radiation protection dosemeters and doserate meters and gives recommendations for establishing these quantities. For individual monitoring, it covers whole body and extremity dosemeters (including those for the skin and the eye lens), and for area monitoring, portable and installed dosemeters. Guidelines are given for the calibration of dosemeters and doserate meters used for individual and area monitoring in reference radiation fields. Recommendations are made for the position of the reference point and the phantom to be used for personal dosemeters. ISO 29661:2012 also deals with the determination of the response as a function of radiation quality and angle of radiation incidence. ISO 29661:2012 is intended to be used by calibration laboratories and manufacturers.

ISO 12789-2:2008 describes the characterization of simulated workplace neutron fields produced by methods described in ISO 12789-1. It specifies the procedures used for establishing the calibration conditions of radiation protection devices in neutron fields produced by these facilities, with particular emphasis on the scattered neutrons. The diversity of workplace neutron fields is such that several special facilities have been built in order to simulate them in the laboratory. In ISO 12789-2:2008, the neutron radiation field specifications are classified by operational quantities. General methods for characterizing simulated workplace neutron fields are recommended.

ISO 12789-2:2008 describes the characterization of simulated workplace neutron fields produced by methods described in ISO 12789-1. It specifies the procedures used for establishing the calibration conditions of radiation protection devices in neutron fields produced by these facilities, with particular emphasis on the scattered neutrons. The diversity of workplace neutron fields is such that several special facilities have been built in order to simulate them in the laboratory. In ISO 12789-2:2008, the neutron radiation field specifications are classified by operational quantities. General methods for characterizing simulated workplace neutron fields are recommended.

ISO 6980-3:2006 describes procedures for calibrating and determining the response of dosemeters and doserate meters in terms of the International Commission on Radiation Units and Measurements (ICRU) operational quantities, that is, the directional dose equivalent and the personal dose equivalent, for radiation protection purposes. In addition to the description of calibration procedures, this part of ISO 6980-3:2006 includes recommendations for appropriate phantoms and the way to determine appropriate conversion coefficients. Guidance is provided on the statement of measurement uncertainties and the preparation of calibration records and certificates.

ISO 6980-1:2006 specifies the requirements for reference beta radiation fields produced by radionuclide sources to be used for the calibration of personal and area dosimeters and dose-rate meters to be used for the determination of the quantities Hp(0,07) and H'(0,07), and for the determination of their response as a function of beta particle energy and angle of incidence. It gives the characteristics of radionuclides that have been used to produce reference beta radiation fields, gives examples of suitable source constructions and describes methods for the measurement of the residual maximum beta particle energy and the dose equivalent rate at a depth of 0,07 mm in the International Commission on Radiation Units and Measurements (ICRU) sphere. The energy range involved lies between 66 keV) and 3,6 MeV and the dose equivalent rates are in the range from about 10-5Sv h-1 to at least 10 Sv h-1. In addition, for some sources variations of the dose equivalent rate as a function of the angle of incidence are given. ISO 6980-1:2006 proposes two series of beta reference radiation fields from which the radiation necessary for determining the characteristics (calibration and energy and angular dependence of response) of an instrument can be selected. Series 1 reference radiation fields are produced by radionuclide sources used with beam flattening filters designed to give uniform dose equivalent rates over a large area at a specified distance. The proposed sources of 90Sr + 90Y, 85Kr, 204Tl and 147Pm produce maximum dose equivalent rates of approximately 200 mSv h-1. Series 2 reference radiation fields are produced without the use of beam-flattening filters, which allows large area planar sources and a range of source-to-calibration plane distances to be used. Close to the sources, only relatively small areas of uniform dose rate are produced but this series has the advantage of extending the energy and dose rate ranges beyond those of series 1. The radionuclides used are those of series 1 with the addition of the radionuclides 14C and 106Ru + 106Rh; these sources produce dose equivalent rates of up to 10 Sv h-1.

ISO 6980-2:2004 specifies methods for the measurement of the directional absorbed-dose rate in a tissue-equivalent slab phantom in the ISO 6980 reference beta-particle radiation fields. The energy range of the beta-particle-emitting isotopes covered by these reference radiations is 0,066 to 3,54 MeV (maximum energy). Radiation energies outside this range are beyond the scope of this standard. While measurements in a reference geometry (depth of 0,07 mm at perpendicular incidence in a tissue-equivalent slab phantom) with a reference class extrapolation chamber are dealt with in detail, the use of other measurement systems and measurements in other geometries are also described, although in less detail. The ambient dose equivalent, H*(10) as used for area monitoring of strongly penetrating radiation is not an appropriate quantity for any beta radiation, even for that penetrating a 10 mm thick layer of ICRU tissue (i.e. Emax greater than 2 MeV). If adequate protection is provided at 0,07 mm, only rarely will one be concerned with other depths, for example 3 mm. ISO 6980-2:2004 is geared towards organizations wishing to establish reference-class dosimetry capabilities for beta particles, and serves as a guide to the performance of dosimetry with the reference class extrapolation chamber for beta-particle dosimetry in other fields. Guidance is also provided on the statement of measurement uncertainties.

This part of ISO 8529 specifies the reference neutron radiations, in the energy range from thermal up to 20 MeV, for calibrating neutron-measuring devices used for radiation protection purposes and for determining their response as a function of neutron energy. Reference radiations are given for neutron fluence rates of up to 1 _ 109 m?2_s?1, corresponding, at a neutron energy of 1 MeV, to dose-equivalent rates of up to 100 mSv_h?1. This part of ISO 8529 is concerned only with the methods of producing and characterizing the neutron reference radiations. The procedures for applying these radiations for calibrations are described in ISO 8529-2 and ISO 8529-3. The reference radiations specified are the following: _ neutrons from radionuclide sources, including neutrons from sources in a moderator; _ neutrons produced by nuclear reactions with charged particles from accelerators; _ neutrons from reactors. In view of the methods of production and use of them, these reference radiations are divided, for the purposes of this part of ISO 8529, into the following two separate sections. _ In clause 4, radionuclide neutron sources with wide spectra are specified for the calibration of neutronmeasuring devices. These sources should be used by laboratories engaged in the routine calibration of neutron-measuring devices, the particular design of which has already been type tested. _ In clause 5, accelerator-produced monoenergetic neutrons and reactor-produced neutrons with wide or quasi monoenergetic spectra are specified for determining the response of neutron-measuring devices as a function of neutron energy. Since these reference radiations are produced at specialized and well equipped laboratories, only the minimum of experimental detail is given. For the conversion of neutron fluence into the quantities recommended for radiation protection purposes, conversion coefficients have been calculated based on the spectra presented in normative annex A and using the fluence-to-dose-equivalent conversion coefficients as a function of neutron energy as given in ICRP Publication 74 and ICRU Report 57.

ISO 8769:2010 specifies the characteristics of reference sources of radioactive surface contamination, traceable to national measurement standards, for the calibration of surface contamination monitors. ISO 8769:2010 relates to alpha-emitters, beta-emitters and photon emitters of maximum photon energy not greater than 1,5 MeV. It does not describe the procedures involved in the use of these reference sources for the calibration of surface contamination monitors. ISO 8769:2010 specifies also reference radiation for the calibration of surface contamination monitors, which takes the form of adequately characterized large area sources specified, without exception, in terms of surface emission rates, the evaluation of these quantities being traceable to national standards.

ISO 4037-4:2004 gives guidelines on additional aspects of the characterization of low energy photon radiations. ISO 4037-4:2004 also describes procedures for calibration and determination of the response of area and personal dose(rate)meters as a function of photon energy and angle of incidence. ISO 4037-4:2004 concentrates on the accurate determination of conversion coefficients from air kerma to Hp(10) and H*(10) for the spectra of low energy photon radiations. As an alternative to the use of conversion coefficients, the direct calibration in terms of these quantities by means of appropriate reference instruments is described.

Specifies the characteristics and production methods of X and gamma reference radiation for calibrating dosemeters and rate dosemeters at air kerma rates from 10 Gy/h to 10 Gy/h and for determining their response as a function of photon energy.

Specifies procedures for the calibration of neutron-measuring devices used for radiation protection purposes, and for determining their response as a function of energy, angle of incidence and dose equivalent rate, using the neutron reference radiations according to ISO 8529.

Specifies the characteristics of reference sources for the calibration of surface contamination monitors that are traceable to national measurement standards. Relates to a series of sources emitting electrones of energy less than 0,15 MeV and photons of energy less than 1,5 MeV.

Specifies the characteristics of reference sources and reference radiations which take the form of adequately characterized large-area sources specified in terms of activity (per unit area) and surface emission rate. Regulatory documents refer to surface contamination in terms of activity per unit area, while the response of monitoring instruments is related directly to the radiation emitted (i.e. they indicate surface emission rate). Does not describe the procedure involved in the use of these sources (see e.g. IEC Publication 325).